Posterior retractor



FIG. 1 is a perspective view of a posterior retractor according to the present ornamental design.

FIG. 2 is a first end plan view of the posterior retractor shown in FIG. 1.

FIG. 3 is a top view of the posterior retractor shown in FIG. 1.

FIG. 4 is a side view of the posterior retractor shown in FIG. 1; and,

FIG. 5 is a second end plan view of the posterior retractor shown in FIG. 1. 

The ornamental design for a posterior retractor, as shown and described. 